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Science Forum Index » Electronics - Basics Forum » current amplifier question (with a little LabVIEW)
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Message |
| panfilero |
 Posted: Thu Jan 25, 2007 5:41 pm |
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Guest
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Hello, I need to design a current amplifier. I'm trying to design a
virtual instrument in LabVIEW to which I can type in a current (for
example 1.5 Amps) and then have that current realized at the output of
a current amplifier. I believe LabVIEW will provide a small voltage
which I can feed into the current amplifier and then use the output of
that.
I'm going to be using this to drive a real small load of only 15 Ohms.
and would like to be able to push 2 Amps through it (this would be my
maximum current). I think I will be driving the amplifier wtih
millivolts from that DAQ. So I guess this would be the same as having
a 30 Volt output?
This is the first time I've ever attempted to design an amlifier and
was wondering if anyone could give me a little guidance or point me in
the right direction. I think what I'm trying to make is a: voltage
controlled current amplifier. I was wondering
1) Where should I be looking for something like this, at Op-Amps,
FETs, BJTs?
2) Whats the difference between a current amplifier and a voltage
amplifier, in this case it seems like you could describe this as
either.
appreciate any help i could get with this
thanks
joshua |
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| Joerg |
| Posted: Thu Jan 25, 2007 5:54 pm |
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panfilero wrote:
Quote: Hello, I need to design a current amplifier. I'm trying to design a
virtual instrument in LabVIEW to which I can type in a current (for
example 1.5 Amps) and then have that current realized at the output of
a current amplifier. I believe LabVIEW will provide a small voltage
which I can feed into the current amplifier and then use the output of
that.
I'm going to be using this to drive a real small load of only 15 Ohms.
and would like to be able to push 2 Amps through it (this would be my
maximum current). I think I will be driving the amplifier wtih
millivolts from that DAQ. So I guess this would be the same as having
a 30 Volt output?
This is the first time I've ever attempted to design an amlifier and
was wondering if anyone could give me a little guidance or point me in
the right direction. I think what I'm trying to make is a: voltage
controlled current amplifier. I was wondering
1) Where should I be looking for something like this, at Op-Amps,
FETs, BJTs?
2) Whats the difference between a current amplifier and a voltage
amplifier, in this case it seems like you could describe this as
either.
That's a lot of current. Opamps don't do that much. You didn't mention
the max frequency. If audio or at least under 50kHz you could look at
larger audio amps. National, TI etc. Else you'd have to follow the opamp
with some beefy transistors. Driver chips such as the LH0063 and LH0033
have unfortunately become almost extinct. I kept a few just in case but
I wouldn't design a new circuit with these. Also, don't forget a rather
large heat sink if this needs to operate more than a few seconds ;-)
--
Regards, Joerg
http://www.analogconsultants.com |
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| Genome |
| Posted: Thu Jan 25, 2007 6:31 pm |
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Guest
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"panfilero" <panfilero@gmail.com> wrote in message
news:1169761279.767237.167960@v45g2000cwv.googlegroups.com...
Quote: Hello, I need to design a current amplifier. I'm trying to design a
virtual instrument in LabVIEW
appreciate any help i could get with this
thanks
joshua
End of story then.
You have to buy the appropriate hardware modules from National Instruments.
So, not only do you get a shitty visual programming language you also have
to shell out $84121.54 for the rest of the stuff.......
Bummer
DNA |
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| Matthew Beasley |
| Posted: Thu Jan 25, 2007 7:27 pm |
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If you're after low development cost and time, check out
http://www.apexmicrotech.com
They make real big opamps, but be prepared to pay through the nose for them. |
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| John Popelish |
| Posted: Thu Jan 25, 2007 9:25 pm |
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Guest
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panfilero wrote:
Quote: Hello, I need to design a current amplifier. I'm trying to design a
virtual instrument in LabVIEW to which I can type in a current (for
example 1.5 Amps) and then have that current realized at the output of
a current amplifier. I believe LabVIEW will provide a small voltage
which I can feed into the current amplifier and then use the output of
that.
I'm going to be using this to drive a real small load of only 15 Ohms.
and would like to be able to push 2 Amps through it (this would be my
maximum current). I think I will be driving the amplifier wtih
millivolts from that DAQ. So I guess this would be the same as having
a 30 Volt output?
This is the first time I've ever attempted to design an amlifier and
was wondering if anyone could give me a little guidance or point me in
the right direction. I think what I'm trying to make is a: voltage
controlled current amplifier. I was wondering
1) Where should I be looking for something like this, at Op-Amps,
FETs, BJTs?
2) Whats the difference between a current amplifier and a voltage
amplifier, in this case it seems like you could describe this as
either.
We are not there, yet.
Will the signal in and out unidirectional or bidirectional?
What will be the maximum frequency or time rate of change of
the output current?
Must one end of the 15 ohm load be grounded or connected to
some other voltage, or is it a two terminal device that you
can connect to your driver as needed? |
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| Ban |
| Posted: Fri Jan 26, 2007 5:00 am |
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Guest
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panfilero wrote:
Quote: Hello, I need to design a current amplifier. I'm trying to design a
virtual instrument in LabVIEW to which I can type in a current (for
example 1.5 Amps) and then have that current realized at the output of
a current amplifier. I believe LabVIEW will provide a small voltage
which I can feed into the current amplifier and then use the output of
that.
I'm going to be using this to drive a real small load of only 15 Ohms.
and would like to be able to push 2 Amps through it (this would be my
maximum current). I think I will be driving the amplifier wtih
millivolts from that DAQ. So I guess this would be the same as having
a 30 Volt output?
This is the first time I've ever attempted to design an amlifier and
was wondering if anyone could give me a little guidance or point me in
the right direction. I think what I'm trying to make is a: voltage
controlled current amplifier. I was wondering
1) Where should I be looking for something like this, at Op-Amps,
FETs, BJTs?
2) Whats the difference between a current amplifier and a voltage
amplifier, in this case it seems like you could describe this as
either.
appreciate any help i could get with this
thanks
joshua
Me thinks it will be better for you to buy some prefabricated modules,
because a current amp with that power is not an easy project.
If you need only an unipolar and slowly changing signal, a programmable
power supply would probably be the easiest. It could be set in current
limiting mode and can be adressed via RS232 (or USB).
If the output shall be bipolar and of higher frequency content, you can
easily modify an DC-coupled audio amp like those vintage Crown DC350A, if
there is the possibility of putting a small sense resistor in the gnd-leg of
your load.
I don't see how LabView can provide "some small voltage" without extra
hardware.
Everything else (fix gnded, floating) is also possible but requires some
additional circuitry.
At the end, why don't you descibe your load a bit better, or what you want
to achieve? I'm sure you'll get much more useful responses.
--
ciao Ban
Apricale, Italy |
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